Communication with an audience typically requires the presentation of sound or images. Public spaces for communication often have poor acoustic qualities. Ambient noise or resonant properties of construction materials and dimensions in, for example, concert halls, open air venues, small rooms, and retail spaces can make the presentation of desirable sound quality difficult. The presentation of visual images is typically done by displaying of signs or video, for example, by putting a TV monitor in a public space. The control of sound is typically done by “brute force” methods such as, for example, avoiding feedback in PA systems by simply turning the volume down.